If $a + b = -9$ and $x + y = -3$, what is $-3b - 5x - 5y - 3a$ ?
Explanation: $= -3a - 3b - 5x - 5y$ $= (-3) \cdot (a + b) + (-5) \cdot (x + y)$ $= (-3) \cdot (-9) + (-5) \cdot (-3)$ $= 27 + 15$ $= 42$